1. Field of the Invention
This invention relates to an improvement in a speed instruction generating system for an elevator, which use an electronic computer to generate speed instruction data for the elevator.
2. Description of the Prior Art
Heretofore, for an elevator to run smoothly, the acceleration operation has been controlled according to the difference between an acceleration instruction signal increasing with time and an output signal of a tachometer generator coupled to the elevator cage, and the deceleration operation has been controlled according to the difference between the output of the tachometer generator and a deceleration instruction signal which decreases as the cage approaches the desired floor.
In order to improve the deceleration characteristics, it is necessary to provide a number of position data for the deceleration instruction data signal. In order to meet this requirement, the use of a number of expensive position detectors is necessary, which results in an increase in manufacturing cost and a decrease in reliability.
In order to overcome this difficulty, a method has been proposed in which a signal proportional to a speed of a hoisting motor is counted, or integrated. The result of the count is decoded by a decoder, the output of which is stored by a latch circuit, so that the signals proportional to the speed of the motor are accumulated to detect a cage position, to thereby reduce the number of position detectors.
In such a system, when a signal proportional to the speed of the hoisting motor is inputted, the counter is made ready for counting the signal, but the system is arranged so that the signal proportional to the speed of the motor is not inputted to the counter until the cage has reached a deceleration start point; that is, when the cage has reached the deceleration start point, the signal is then inputted so as to be counted, to thereby detect the cage position.
However, it should be noted that in such a system, from the view point of the passenger's comfort, the deceleration pattern should be determined so that the acceleration and deceleration are substantially constant, and therefore the relation between the cage stopping distance and the speed is substantially a square root curve. Accordingly, adjustment of the counter and decoder which counts the pulses to provide a speed curve is intricate, which unavoidably results in a significant increase in the manufacturing cost.